Lung cancer is the number one cause of cancer mortality in the United States, accounting for more than 135,000 deaths annually (1). Prevention of this disease would have a significant impact on overall cancer mortality. Smoking prevention and cessation is one control strategy to reduce lung cancer deaths. However, approximately 15% of all lung cancer deaths, or an estimated 20,000 deaths annually, are not directly attributable to smoking (2). Consequently, strategies to prevent these lung cancer deaths are unclear. In this study we propose to analyze an existing data set to evaluate dietary beta-carotene as a potential protective factor against the development of lung cancer in nonsmokers. The proposed study involves analysis of existing data collected from a population-based case-control epidermiologic study comparing 439 nonsmoking lung cancer cases (former and never smokers) to 439 nonsmoking controls matched for age, sex, residence and smoking status (former vs. never). Cases and controls were similarly interviewed and information was collected concerning dietary retinol and beta-carotene, passive smoke and other tobacco exposures, history of occupational and environmental exposures, and medical and family history. All cases of lung cancer were histologically confirmed. Analysis of this data will allow us: (a) to determine whether dietary beta- carotene is protective against lung cancer in a low-risk (nonsmoking) population; (b) to assess the risk associated with passive smoke exposure in the largest case-control study of this type of which we are aware; (c) to evaluate occupational and other exposures which may be involved in the etiology of lung cancer in nonsmokers, and (d) to assess family and medical history as a risk control strategies for nonsmokers. Moreover, these results may have implications for cancer control strategies for smokers, as this analysis may suggest factors other than smoking that may be important in the etiology of lung cancer in smokers, but that may be overshadowed by the substantial risk associated with smoking.